The human and mouse sperm proteomes will be determined using whole-cell mass spectroscopy (WC-MS) of purified sperm samples. WC-MS has recently been pioneered in the Karr laboratory and we have analyzed the evolutionary dynamics of the D. melanogaster sperm proteome. Preliminary results using WC- MS demonstrate the utility of this approach for mammalian sperm. Mammalian sperm proteomes will be functionally annotated and otholog relationships determined. Comparative analyses of all three proteomes will greatly restrict the number of candidate loci which possibly underly structural and functionaldifferences of sperm between these widely studied organisms. Commonalities and differences between the mammalian proteomes will identify mouse genes for future studies of spermatogenesis and sperm function. Additionally, inter- and intraspecific evolutionary analyses of the genes encoding the sperm proteome will be used to elucidate the extent of selection upon male reproductive genes. As the first mammalian cellular proteomes to be determined, this research should provide a useful experimentaltemplate for future proteomic studies in addition to providing a resource for the study of the genetic basis of male infertility.